A few lizards have tails that can break off when predators attack, and then grow an extension back again.
The new growth is cartilage, not bone like the original tail.
While this may seem like a cool thing to show to the neighborhood gang of kids, this parlor trick comes at great cost to the lizard.
A lizard’s tail is made up of vertebrae, much like our backbones. The tails, however, have specialized vertebrae with fine cracks below each joint where they fit together.
Think of those fine lines as dotted lines on tear-away coupons.
The muscles surrounding these dotted-line areas are thin and can be easily torn without causing significant damage to the muscle fiber around them.
Many lizards will frantically wiggle their tails when in danger, hoping predators will grab that end instead of their heads or bodies which would cause immediate death. Some lizards’ tails are even brightly colored, to add to their attractiveness.
If a predator, including those of the curious-fifth-grader variety, grabs the wriggling tail, the tail will snap off where the bone and muscle are weak, and the lizard may escape.
It’s an amazing act of nature, but as mentioned, it costs the lizard dearly. Some die later from the trauma.
Also, the energy required to heal the wounds and grow the cartilage might be better used to last through a food shortage or some other natural catastrophe.